Solvents have been playing important roles in many applications, for example, in paints and coatings, printing inks, adhesives, cosmetics, and pharmaceuticals. Global solvents utilization is around 20 million tonnes in 2011 and demand is predicted to grow an average of 2.5% annually. The demand may be expected to reach 25 million tonnes in 2019 with expected revenues increasing to 25 billion euros.
Aliphatic solvents are one of the solvent groups which can refer to hydrocarbon solvents comprising paraffins (straight chains), isoparaffins (branch chains) and naphthenes (non-aromatic rings). Aliphatic solvents account for more than 2.64 million tonnes in 2011, or around 13% of global solvents consumption. Aliphatic solvents are mainly produced from crude oil. They can be produced through several physical processes used in petrochemical industry starting from crude oil distillation, cracking, alkylation, isomerization, reforming and other operations.
Several separation techniques are available such as, for example, distillation, absorption, liquid-liquid extraction, drying, leaching, crystallization and gas adsorption. However, 95% of liquid separations are conducted by distillation processes. This is due to the fact that other alternative separation techniques, such as absorption, adsorption, and extraction, can require the addition of an external substance, for example, entrainer, solvent and adsorbent to create two phases for separation. This external substance has to then be removed. While in the distillation, the principle is based on the difference in composition between liquid mixture and the vapor formed by different volatilities of the components presented in the mixtures. Moreover, distillation can be the least expensive of possible methods for separating a given mixture, and in many cases it is the only feasible method.